1. Field of Invention
The present invention relates to a method for fabricating a nanocomposite material. More particularly, the present invention relates to a method for fabricating a polybenzoxazole (PBO)/clay nanocomposite material.
2. Description of Related Art
Polybenzoxazoles (PBOs) are a class of polymers that have excellent thermal stability, high mechanical strength and chemical resistance. The general molecular structure of PBOs is shown in the following:
wherein X, Y can be O, C(CF3)2, C(CH3)2, CO, etc. These properties of PBOs are similar to those polymers with high thermal resistance, such as, polyimides. Unlike polyimides, PBOs do not possess a polar carbonyl group. Therefore, PBOs have low water absorption and a low dielectric constant. These special attributes allow PBOs to be more applicable in the microelectronic industry, for example, as buffer coatings in IC chip, interlayer dielectrics for multichip modules (MCM-D), substrates for flexible printed circuit board, tape automatic bonding material and high-end electronic packaging materials.
However, similar to other polymeric materials in general, the thermal expansion coefficient of PBOs is higher than that of the organic materials or metallic materials (such as, silicon chip, copper foil, etc.). Due to the mismatch in the thermal expansion coefficients, when PBOs are used with the above materials, the generation of thermal stress would cause warpage and cracking in the products. The current approach in addressing the problem of high thermal expansion coefficient of PBOs involves using molecular design to adjust the molecular structure of PBOs. However, the aforementioned conventional method involves the synthesis of new monomers, which is expensive and time-consuming.